How I got my 2005 Scion tC ready for a California Smog check in 12 hours

I tried to start up my 2005 Scion tC to drive it for a smog check, and the battery was dead.  I replaced the battery, but that cleared the ECU memory, meaning that the ODBII reader reported that the emissions tests were "NOT READY".

Most of the internal tests are easy to pass, but the infamously difficult ones to clear the test are the Catalytic Converter, and Evap tests.  Here's how I got both tests in the "ready" state in 12 hours:

• I started the car, warmed it up by driving it around for about 10 minutes, and then drove between 40-50 MPH for 7 minutes, trying my best not to stop or deviate from that speed range.  I found a road with a 45 MPH speed limit that went on for about 5-6 miles, with not many signal lights.  If you run into a few signal lights, you still might pass the test.  Then, the second part of the test is driving between 35-45 MPH for another 7 minutes.   Basically try to drive between 40-45 MPH for 14 minutes.  To my surprise, the Catalytic Converter passed, according to the ODBII reader I had.  I have another car that is having a hard time passing the Catalytic Converter test, but I think that car has a bad thermostat.  The Catalytic Converter test has to run at a certain temperature range.
• Next was getting the Evap test ready.  This was more challenging.  I stopped the engine, opened the gas cap, then started the engine.  I got the temperature up again, and then idled in park at 3500-4000 RPM for 12 seconds (at least 10).  Then I drove the car around for 15-50 minutes, turning on the A/C or front defroster when I ran into traffic or hit a red light.  This test didn't work, because you also have to make sure that the car engine is completely cooled before you start this test.  I waited 8 hours, and tried the test again.  weather.com said my city was 39 degrees, so I was worried the test wouldn't pass.  I heard that the temp has to be at least 40 degrees, or you can run the test twice if the temperature is less than 40 degrees (spaced 8 hours apart).  I went out, opened the gas cap and closed it, started the car to get it warmed up, and then plugged in the ODBII reader while the car was still on.  To my surprise, the Evap test was ready when I checked, after about 5 minutes of idling.  I was really surprised I didn't have to rev the engine again and let the car idle (with the A/C or defroster on) for 15-50 minutes.  I that what happened was that part of the test was completed 8 hours prior, but the car still needed to do the other part of the test, involving a cold engine start.

Now, the ODBII reader says the car is "ready" for all the tests, after about 12 hours.  I just need to do the actual test now, and hope that it passes!

How to clear P0128 Check Engine Light (CEL) (coolant temperature below thermostat regulating temperature) on a 1999, 2000, 2001, or 2002 Toyota Corolla

Parts needed:

• Temperature sensor: http://www.ebay.com/itm/271937021784
• 19mm deep socket: http://www.homedepot.com/p/Husky-3-8-in-Drive-19-mm-6-Point-Metric-Deep-Socket-H3D6PDP19MM/202913533
• 10mm socket
• Mini flathead screwdriver

Do this:

1. Park car in a place where you don't mind a little coolant leaking out, or put a basin under your car
2. Pop hood
3. Disconnect battery  (Disconnect black/negative first)
4. Remove battery from car
5. Remove engine air filter and air filter console.  You don't have to completely remove the top of the air filter console.  You can just move it off to the side. See https://www.youtube.com/watch?v=sXUNb9fTeG8 - you might need to remove two black plastic cable straps/ties which you can do by sticking in a mini flathead screwdriver in the opposite side (from the bottom).  Be careful not to drop any 10mm bolts down the hole in the air filter console.  You can wrap it in aluminum foil if you don't trust yourself.
6. Use your hands to unclip the wiring from the old temperature sensor.  It might be a tight fit, but you should be able to get your fingers in there if your fingers aren't too fat.  Be careful not to break the sensor wirings.
7. Remove the temperature sensor using the 19mm deep socket.  I used a breaker bar.
8. Some coolant might leak out, so quickly hand-screw in the new temperature sensor into the engine and tighten with the 19mm deep socket.
9. Reassemble.

The check engine will be cleared because the battery was removed, but the real test will take 50-200 miles of driving to make sure the car's computer keeps the P0128 code off.

Some people reported the temperature dial instantly going up to "H" right away, but I didn't experience that.